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Arthritis Care Res (Hoboken). 2015 Oct;67(10):1345-53. doi: 10.1002/acr.22606.

Determining the Minimally Important Difference in the Clinical Disease Activity Index for Improvement and Worsening in Early Rheumatoid Arthritis Patients.

Author information

1
University of Alabama at Birmingham.
2
St. Joseph's Health Center and Western University, London, Ontario, Canada.
3
Mount Sinai Hospital/University of Toronto, Toronto, Ontario, Canada.
4
Centre Hospitalier de l'Université de Montreal, Montreal, Quebec, Canada.
5
Centre Hospitalier Universitaire de Sherbrooke and Université de Sherbrooke, Sherbrooke, Quebec, Canada.
6
Southlake Regional Health Centre, Newmarket, Ontario, Canada.
7
University of Manitoba, Winnipeg, Manitoba, Canada.
8
Johns Hopkins University, Baltimore, Maryland.
9
Centre Hospitalier de l'Université de Montreal, Montreal, Quebec, Canada, and Hospital for Special Surgery, New York, New York.

Abstract

OBJECTIVE:

Simplified measures to quantify rheumatoid arthritis (RA) disease activity are increasingly used. The minimum clinically important differences (MCID) for some measures, such as the Clinical Disease Activity Index (CDAI), have not been well-defined in real-world clinic settings, especially for early RA patients with low/moderate disease activity.

METHODS:

Data from Canadian Early Arthritis Cohort patients were used to examine absolute change in CDAI in the first year after enrollment, stratified by disease activity. MCID cut points were derived to optimize the sum of sensitivity and specificity versus the gold standard of patient self-reported improvement or worsening. Sensitivity, specificity, positive predictive values, and negative predictive values were calculated against patient self-reported improvement (gold standard) and for change in pain, Health Assessment Questionnaire (HAQ), and Disease Activity Score in 28 joints (DAS28) improvement. Discrimination was examined using the area under receiver operator curves. Similar methods were used to evaluate MCIDs for worsening for patients who achieved low disease activity.

RESULTS:

A total of 578 patients (mean ± SD age 54.1 ± 15.3 years, 75% women, median [interquartile range] disease duration 5.3 [3.3, 8.0] months) contributed 1,169 visit pairs to the improvement analysis. The MCID cut points for improvement were 12 (patients starting in high disease activity: CDAI >22), 6 (moderate: CDAI 10-22), and 1 (low disease activity: CDAI <10). Performance characteristics were acceptable using these cut points for pain, HAQ, and DAS28. The MCID for CDAI worsening among patients who achieved low disease activity was 2 units.

CONCLUSION:

These minimum important absolute differences in CDAI can be used to evaluate improvement and worsening and increase the utility of CDAI in clinical practice.

PMID:
25988705
PMCID:
PMC4580563
DOI:
10.1002/acr.22606
[Indexed for MEDLINE]
Free PMC Article

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